New Rockstars has an interesting video up pointing to some compelling evidence of Maria Hill being a Skrull. Basically:
-Fury limped in front of Maria when he got back down to Earth
-Next scene, Pagon told Gravik that Fury was walking with a limp
-When Falsworth mentioned the dirty bomb dealer (mentioning only one of five they had located), you could see Hill take notes
-Next scene, Gi'ah gets the same location to go buy the dirty bomb
-Fury and Talos conveniently get there what seems to be moments later
-Fury didn't seem all that upset about Maria on the train back with Talos
They easily could've faked her death, and having her say "It was you" to Fury as he watched her 'die' is pretty good psychological warfare. Except this is Fury and you ain't foolin' him.
Now why Fury would allow the plan to move forward and allow that bomb to go off, assuming he is several steps ahead, is another question